1. Technical Field
The present invention relates to a liquid discharge apparatus, a head unit, a capacitive load drive circuit, and an integrated circuit device for capacitive load drive.
2. Related Art
In a liquid discharge apparatus such as an ink jet printer which prints an image or a document by discharging an ink, a liquid discharge apparatus using a piezoelectric element (for example, a piezo element) is known. The piezoelectric elements are respectively arranged by correlating with a plurality of nozzles in a head unit, and each thereof are driven in accordance with a drive signal. Thereby, a predetermined amount of the ink (liquid) is discharged at a predetermined timing from the nozzle, and dots are formed. Since the piezoelectric element is a capacitive load such as a capacitor if being electrically viewed, there is a need to supply a sufficient current in order to operate the piezoelectric element of each nozzle.
Therefore, in the liquid discharge apparatus described above, a configuration of driving the piezoelectric element by supplying the drive signal which is amplified by an amplification circuit to the head unit (ink jet head), is made. As an amplification circuit, a system of performing the current amplification of a source signal before the amplification by a Class AB amplifier or the like is used, but since energy efficiency is poor, a Class D amplifier is offered in recent years (see JP-A-2010-114711).
In order to obtain the discharge accuracy (an output waveform is made to be highly accurate) in the Class D amplifier for the ink jet head, a high oscillation frequency (1 MHz to 8 MHz) which is 20 times or more in comparison with the Class D amplifier for an audio, is necessary. However, there is a feature of being likely to be affected by various types of noises due to the high oscillation frequency. Therefore, the inventors of the invention have been found that a component layout of an IC of which importance to be checked is small in the Class D amplifier for the audio, is important for a noise reduction in the Class D amplifier for the ink jet head.